Tendons that move fingers are held in place on bones by a series of ligaments called pulleys (or sheath). These ligaments form an arch on a bone surface that creates a fibrous tunnel through which the tendon extends along the extent of the bone. Triggering is usually the result of a thickening in the tendon that forms a nodule, or knob. The pulley ligament may thicken as well. The constant irritation from the tendon repeatedly sliding through the pulley causes the tendon to swell in this area and create the nodule.
The symptoms of trigger finger include pain and a painful clicking sensation when the finger is bent. Pain usually occurs when the finger is bent and straightened. Tenderness usually occurs over the area of the nodule. The clicking sensation occurs when the nodule moves through the tunnel formed by the pulley ligaments. With the finger straight, the nodule is at the far edge of the surrounding ligament. When the finger is flexed, the nodule passes under the ligament and causes the clicking sensation. If the nodule becomes too large it may pass under the ligament and become stuck at the near edge. The nodule cannot move back through the tunnel causing the finger to lock in the flexed trigger position. Surgery may be required to release the trigger finger.
Trigger finger and tendon sheath surgery are common procedures that are usually performed in the operating room. A traditional tendon sheath release procedure is performed in an operating room at a hospital or surgery center under conscious sedation—which involves risk to the patient—and using a local anesthetic. The traditional open operation uses a conventional scalpel device and a 1.5 to 2.0 cm incision that disrupts all tissue and skin above the pulley and requires two or three stitches.
In U.S. patent application Ser. No. 12/896,088, incorporated herein by reference, Applicants disclosed a device and method for tendon sheath surgery that allows the operation to be performed in a surgeon's office safely, quickly, and in a less costly manner than going to the operating room. The current invention is an improvement upon the device disclosed in U.S. patent application Ser. No. 12/896,088 to ensure that other tissue is not damaged while the pulley is severed.